Japanese Unexamined Published Patent Application No. 4- 304393 and Japanese Unexamined Published Patent Application No. 4- 354890, have already given a description regarding a method wherein impurities in a supplied electrolyte solution are removed, for the purification of waste solution which accompany industrial production. In this method, an electrolytic bath is used which includes an ion-selective diaphragm between an anode and a cathode, the electrolyte solution to be electrolyzed is supplied in the area between the anode and the diaphragm (hereunder referred to as "anode chamber"), the cationic metal ion contained in the electrolyte solution is subjected to electrophoresis towards the cathode end through the diaphragm for separation, and the matter separated into a cathode chamber with the cathode provided therein is separated using some sort of separating apparatus.
If the anode chamber solution, which is supplied to the anode chamber in a circulatory manner, can be controlled so that the separated matter is converted into a more usable form upon separation, then a major contribution will have been made to the industrial field.
If a cation-selective membrane is employed as the diaphragm, then usually the free acid radical is separated into the anode chamber, while the anionic metal ion is converted into the hydroxide form of the metal by the alkalinity generated by charging and dissociation of the water, and thus a glutinous, dark-green, amorphous matter is produced in the cathode chamber. However, no effective method has been discovered for controlling, as desired, the properties of the matter produced in this manner.
Also, it is publicly known that viscous hydroxides are produced in the cathode chamber, and regarding given metal ion species, it is known that reducing metal particles of indefinite diameter are obtained on the cathode surface. Nevertheless, the production has not been realized for a wider range of metal species in the cathode chamber.
Measures for the prevention of environmental pollution have been applied for years. However, at the same time, waste matter has been generated as a secondary product of these preventive measures, for which no utility value has been found, and the disposal of this waste matter has become a problem. In other words, it has been believed that the production of waste matter in environmental pollution prevention measures is unavoidable.